Modeling Of Rocket Structural Dynamics And Analysis Of Modal Deviation

Rocket is the basic tool for space exploration and an important symbol of the comprehensive strength of the country.Dynamic characteristic analysis of full-scale rocket is the basis of attitude control system design and load analysis,and plays an important role in the overall design of rocket.However,on the one hand,with the increase of the size and weight of the rocket,the cost of full-scale rocket modal test is higher and higher,and the difficulty is greater and greater;on the other hand,in engineering practice,there is a certain degree of uncertainty,especially for rocket as an extremely complex structural system.Therefore,how to efficiently and accurately establish the dynamic simulation model of rocket and scientifically evaluate the influence of uncertain parameters on the dynamic characteristics of rocket structure is an important subject in the field of rocket modeling and analysis.In order to reduce the influence of modeling deviation of complex substructures,a method of experimental-analytical hybrid modeling based on modal synthesis is proposed in this paper.The modal deviation analysis of structures with uncertain parameters is carried out by using the agent model optimization method.Experimental-analytical hybrid modeling is based on the substructure modal synthesis method.First,experimental substructures are constructed by using the data such as test frequency,mode shapes,etc.And then the substructures of analysis models are replaced and modal synthesis is carried out.In this paper,a one-step method for generating the second coordinate transformation matrix is systematically derived based on the original double-compatible free-interface modal synthesis method,which can be applied to the complex docking of multiple substructures docking to one surface.Three kinds of hybrid modeling schemes are designed,and they are compared and discussed through an example model of the full-scale rocket.The interval parameters are used to describe the uncertainties,and the solution of the natural frequencies of structures with uncertain parameters corresponds to the generalized interval eigenvalue problem.Although the traditional optimization methods such as genetic algorithm can avoid the expansion of the interval and get the high-precision solution,the amount of calculation is very large.In this paper,radial basis agent model(RBF)optimization method is applied to generalized interval eigenvalue problem.The frame structure example is used to compare RBF with matrix perturbation method and genetic algorithm,and then the modal deviation analysis of rocket inertial cabin is carried out to verify the accuracy and efficiency of this method.Based on the Patran Command Language(PCL)and the cross-platform C++ development using QT,a rapid modeling software is developed for the integration modeling of longitudinal and transverse torsion,inertial cabin modeling and strap-on equipment modeling of rocket.The functions of hybrid modeling and modal deviation analysis are integrated into the software,and a set of engineering software used to dynamic modeling and modal deviation analysis for rocket is completed.The verification and testing of software functions are demonstrated by taking the integration modeling module as an example.The software has a good operation interface,runs smoothly,and it has a strong engineering application value.